1. Field of the Invention
The present invention is in the field of integrated circuit (IC) devices and particularly IC devices utilized as memory circuits.
Still more particularly, the present invention pertains to an improved IC device and lead frame subassembly therefor having improved decoupling characteristics and enabling the formation of more compact memory assemblies.
2. The Prior Art
The use of IC devices, particularly as components of memory circuits, is widespread. When one or more of the switching circuit elements of an IC are activated, current and voltage transients are generated, which transients are injected into the power supply circuit which is in turn linked to other elements of the memory system. Where the transient energy of the pulses approaches the characteristics of a functional signal, it is possible to obtain a false reading or transmission of false information, resulting in what is known in the industry as "soft error".
In order to reduce the instances of soft error, it is conventional to employ decoupling or by-passing capacitors bridging the power supply inputs of the IC, whereby transient energy (noise) is absorbed rather than being transmitted to the rest of the IC circuits through the power supply connections.
Heretofore, in circuits employing ICs of the lead frame type, the decoupling has been effected by mounting a capacitor on the printed circuit (PC) board adjacent to and externally of each IC, the leads of the capacitor being connected via the PC wiring across the power supply terminals of the IC. The series combination of lead length and wiring increases the effective impedance of the capacitor, rendering it less effective, especially for shunting high frequency current transients such as are typically produced by dynamic IC memory circuits. Yet, these circuits require that the power supply be maintained .+-.10% to correctly maintain data stored within the memory. The value of the capacitors heretofore required to be employed has been substantial, on the order of 0.1 to 2 mfd.
Capacitors having such relatively high electrical values, in addition to being expensive, are bulky, whereby the desired goal of circuit compactness is frustrated.